1. Field of the Invention
The present invention relates to electrical connectors and more particularly to high I/O density connectors, having a low-mated height.
2. Brief Description of Prior Developments
The drive to reduce the size of electronic equipment, particularly personal portable devices, and to add additional functions to such equipment, has resulted in an ongoing drive for miniaturization of all components, especially electrical connectors. Efforts to miniaturize connectors have included reducing the pitch between terminals in single or double row linear connectors, so that a relatively high number of I/O or other lines can be interconnected by connectors that fit within tightly circumscribed areas on the circuit substrates allotted for receiving connectors. The drive for miniaturization has also been accompanied by a shift in preference to surface mount techniques (SMT) for mounting components on circuit boards. The confluence of the increasing use of SMT and the required fine pitch of linear connectors has resulted in approaching the limits of SMT for high volume, low cost operations. Reducing the pitch of the terminals increases the risk of bridging adjacent solder pads or terminals during reflow of the solder paste.
To satisfy the need for increased I/O density, array connectors have been proposed. Such connectors have a two dimensional array of terminals mounted on an insulative substrate and can provide improved density. However, these connectors present certain difficulties with respect to attachment to the circuit substrates by SMT techniques because the surface mount tails of most, if not all, of the terminals must be beneath the connector body. As a result, the mounting techniques used must be highly reliable because it is difficult to visually inspect the solder connections or repair them, if faulty.
Another problem presented in soldering connectors to a substrate is that connectors often have insulative housings which have relatively complex shapes, for example, ones having numerous cavities. Residual stresses in such thermoplastic housings can result from the molding process, from the build up of stress as a result of contact insertion, or a combination of both. These housings may become warped or twisted either initially or upon heating to temperatures necessary in SMT processes, such as temperatures necessary to reflow the solder balls. Such warping or twisting of the housing can cause a dimensional mismatch between the connector assembly and the PWB, resulting in unreliable soldering because the surface mounting elements, such as solder balls, are not sufficiently in contact with the solder paste or close to the PWB prior to soldering.
U.S. Pat. Nos. 6,024,584, 6,093,035, 6,079,991, 6,164,983, 6,241,535, all to Lemke et al. and U.S. Pat. Nos. 5,975,921, 6,241,536 all to Shuey, all assigned to the assignee of the present invention, are directed to solutions to these design challenges. The Lemke et al. patents and the Shuey patent are specifically incorporated by reference herein, in their entirety. The drive for reduced connector size relates not only to footprint dimensions but also to mated connector height. As electrical equipment shrinks in size, the necessity arises for stacking circuit boards closer together. This invention concerns high density connectors, particularly low profile connectors for reducing the spacing between stacked circuit boards. The Lemke et al. 584"", 035"", 991"", and 983"" patents each show a receptacle connector without a peripheral wall. The receptacle has a snap on plate for protecting female electrical contacts which otherwise would extend above the base of the receptacle.
U.S. Pat. Nos. 5,692,917, 5,746,622 and 5,888,101, illustrate the use of certain types of inserts in electrical connectors. U.S. Pat. No. 5,215,474, shows a certain protector design surrounding pins of a connector. U.S. Pat. No. 5,026,295, shows a certain cover for protecting terminals. U.S. Pat. No. 5,876,217, shows terminals recessed beneath connector housings. U.S. Pat. No. 4,793,816, discloses a two piece protector for use with a connector having exposed terminals. U.S. Pat. No. 5,637,019, shows an electrical connector with exposed electrical contacts.
There is a need for electrical connectors with high I/O (input/output) density and a low profile, which also provide excellent thermal stability during soldering.
Electrical connectors according to the present invention provide high I/O density and a low profile for providing reduced stacking height between circuit boards and improved thermal stability during soldering to a circuit board.
In accordance with a preferred embodiment of this invention, a high density connector comprises a receptacle housing having a base wall and at least one lateral wall defining a cavity. The lateral wall is configured to nest within a plug housing. A high density array of female electrical contacts is arranged in the cavity which are supported in the base wall and extend unsupported above the base wall to a given height. A single piece protection member is arranged in the cavity adjacent the base wall. The protection member has an array of openings in which the electrical contacts extend. The protection member has a thickness selected so that the electrical contacts do not extend beyond an outer face of the protection member.
The electrical contacts deflect upon insertion of a corresponding male contact of the plug housing and the openings are configured to permit full operation of the contacts including such deflection. The protection member preferably comprises a plate like member which is in contact with the base wall of the receptacle.
In accordance with a further preferred embodiment of this invention the at least one lateral wall of the receptacle housing includes at a free edge thereof a guide surface for guiding the receptacle housing into a cavity of the plug housing and the connector further includes a plug housing having a base wall and at least one lateral wall defining a cavity. The lateral wall of the plug housing is preferably configured receive the lateral wall of the receptacle housing in a nested configuration. A high density array of male electrical contacts is arranged in the plug housing cavity. The male contacts are supported in the base wall of the plug housing and extending unsupported above the base wall to a desired height so that when the receptacle housing is nested in the plug housing the male contacts are engaged with the female contacts.